Psychophysical evidence for impaired Magno, Parvo, and Konio-cellular pathways in dyslexic children
Purpose: Dyslexia is one of the most common learning disabilities affecting millions of people worldwide. Although exact causes of dyslexia are not well-known, a deficit in the magnocellular pathway may play a role. We examined possible deficiency of magnocellular, as compared to parvocellular and k...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Knowledge E
2015-01-01
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| Series: | Journal of Ophthalmic & Vision Research |
| Subjects: | |
| Online Access: | http://www.jovr.org/article.asp?issn=2008-322X;year=2015;volume=10;issue=4;spage=433;epage=440;aulast=Ahmadi |
| _version_ | 1811332620718440448 |
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| author | Khazar Ahmadi Hamid Reza Pouretemad Jahangir Esfandiari Ahmad Yoonessi Ali Yoonessi |
| author_facet | Khazar Ahmadi Hamid Reza Pouretemad Jahangir Esfandiari Ahmad Yoonessi Ali Yoonessi |
| author_sort | Khazar Ahmadi |
| collection | DOAJ |
| description | Purpose: Dyslexia is one of the most common learning disabilities affecting millions of people worldwide. Although exact causes of dyslexia are not well-known, a deficit in the magnocellular pathway may play a role. We examined possible deficiency of magnocellular, as compared to parvocellular and koniocellular pathway function by measuring luminance and color perception.
Methods: Visual stimuli consisted of a series of natural images, divided into layers of luminance, red-green and blue-yellow, which probed magnocellular, parvocellular, and koniocellular pathways, respectively. Thirteen children with dyslexia and 13 sex- and age- matched controls performed three psychophysical tasks. In the first task, subjects were instructed to match the contrast of luminance (magno) and red-green (parvo) images to that of the blue-yellow (konio) images. In the second task, subjects detected the isoluminant point of red-green images to probe parvocellular pathway. In the third task, temporal processing was assessed by measuring reaction time and percentage of correct responses in an identification task using four categories of images, activating all three pathways.
Results: The dyslexic group had significantly elevated luminance and color contrast thresholds and higher isoluminant point ratio in comparison to the control group. Furthermore, they had significantly less correct responses than the control group for the blue-yellow images.
Conclusion: We may suggest that dyslexic subjects might suffer from both magnocellular and parvocellular deficits. Moreover, our results show partial impairment of the koniocellular pathway. Thus, dyslexia might be associated with deficits in all three visual pathways. |
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| format | Article |
| id | doaj.art-173235d06c06406eae0b4f7f3d57f8f3 |
| institution | Directory Open Access Journal |
| issn | 2008-322X |
| language | English |
| last_indexed | 2024-04-13T16:39:42Z |
| publishDate | 2015-01-01 |
| publisher | Knowledge E |
| record_format | Article |
| series | Journal of Ophthalmic & Vision Research |
| spelling | doaj.art-173235d06c06406eae0b4f7f3d57f8f32022-12-22T02:39:16ZengKnowledge EJournal of Ophthalmic & Vision Research2008-322X2015-01-0110443344010.4103/2008-322X.176911Psychophysical evidence for impaired Magno, Parvo, and Konio-cellular pathways in dyslexic childrenKhazar AhmadiHamid Reza PouretemadJahangir EsfandiariAhmad YoonessiAli YoonessiPurpose: Dyslexia is one of the most common learning disabilities affecting millions of people worldwide. Although exact causes of dyslexia are not well-known, a deficit in the magnocellular pathway may play a role. We examined possible deficiency of magnocellular, as compared to parvocellular and koniocellular pathway function by measuring luminance and color perception. Methods: Visual stimuli consisted of a series of natural images, divided into layers of luminance, red-green and blue-yellow, which probed magnocellular, parvocellular, and koniocellular pathways, respectively. Thirteen children with dyslexia and 13 sex- and age- matched controls performed three psychophysical tasks. In the first task, subjects were instructed to match the contrast of luminance (magno) and red-green (parvo) images to that of the blue-yellow (konio) images. In the second task, subjects detected the isoluminant point of red-green images to probe parvocellular pathway. In the third task, temporal processing was assessed by measuring reaction time and percentage of correct responses in an identification task using four categories of images, activating all three pathways. Results: The dyslexic group had significantly elevated luminance and color contrast thresholds and higher isoluminant point ratio in comparison to the control group. Furthermore, they had significantly less correct responses than the control group for the blue-yellow images. Conclusion: We may suggest that dyslexic subjects might suffer from both magnocellular and parvocellular deficits. Moreover, our results show partial impairment of the koniocellular pathway. Thus, dyslexia might be associated with deficits in all three visual pathways.http://www.jovr.org/article.asp?issn=2008-322X;year=2015;volume=10;issue=4;spage=433;epage=440;aulast=AhmadiDyslexia; Koniocellular; Magnocellular; Parvocellular |
| spellingShingle | Khazar Ahmadi Hamid Reza Pouretemad Jahangir Esfandiari Ahmad Yoonessi Ali Yoonessi Psychophysical evidence for impaired Magno, Parvo, and Konio-cellular pathways in dyslexic children Journal of Ophthalmic & Vision Research Dyslexia; Koniocellular; Magnocellular; Parvocellular |
| title | Psychophysical evidence for impaired Magno, Parvo, and Konio-cellular pathways in dyslexic children |
| title_full | Psychophysical evidence for impaired Magno, Parvo, and Konio-cellular pathways in dyslexic children |
| title_fullStr | Psychophysical evidence for impaired Magno, Parvo, and Konio-cellular pathways in dyslexic children |
| title_full_unstemmed | Psychophysical evidence for impaired Magno, Parvo, and Konio-cellular pathways in dyslexic children |
| title_short | Psychophysical evidence for impaired Magno, Parvo, and Konio-cellular pathways in dyslexic children |
| title_sort | psychophysical evidence for impaired magno parvo and konio cellular pathways in dyslexic children |
| topic | Dyslexia; Koniocellular; Magnocellular; Parvocellular |
| url | http://www.jovr.org/article.asp?issn=2008-322X;year=2015;volume=10;issue=4;spage=433;epage=440;aulast=Ahmadi |
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